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32 * @(#)freopen.c 8.1 (Berkeley) 6/4/93
33 * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.21 2008/04/17 22:17:54 jhb Exp $
34 * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
37 #include "namespace.h"
38 #include <sys/types.h>
45 #include "un-namespace.h"
46 #include "libc_private.h"
48 #include "priv_stdio.h"
51 * Re-direct an existing, open (probably) file to some other file.
52 * ANSI is written such that the original file gets closed if at
53 * all possible, no matter what.
56 freopen(const char * __restrict file, const char * __restrict mode, FILE *fp)
59 int dflags, flags, isopen, oflags, sverrno, wantfd;
61 if ((flags = __sflags(mode, &oflags)) == 0) {
74 * If the filename is a NULL pointer, the caller is asking us to
75 * re-open the same file with a different mode. We allow this only
76 * if the modes are compatible.
79 /* See comment below regarding freopen() of closed files. */
80 if (fp->pub._flags == 0) {
85 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) {
92 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
93 (oflags & O_ACCMODE)) {
99 if (fp->pub._flags & __SWR)
101 if ((oflags ^ dflags) & O_APPEND) {
103 dflags |= oflags & O_APPEND;
104 if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) {
112 if (oflags & O_TRUNC)
113 ftruncate(fp->pub._fileno, (off_t)0);
114 if (!(oflags & O_APPEND))
115 _sseek(fp, (fpos_t)0, SEEK_SET);
123 * There are actually programs that depend on being able to "freopen"
124 * descriptors that weren't originally open. Keep this from breaking.
125 * Remember whether the stream was open to begin with, and which file
126 * descriptor (if any) was associated with it. If it was attached to
127 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
128 * should work. This is unnecessary if it was not a Unix file.
130 if (fp->pub._flags == 0) {
131 fp->pub._flags = __SEOF; /* hold on to it */
135 /* flush the stream; ANSI doesn't require this. */
136 if (fp->pub._flags & __SWR)
138 /* if close is NULL, closing is a no-op, hence pointless */
139 isopen = fp->_close != NULL;
140 if ((wantfd = fp->pub._fileno) < 0 && isopen) {
141 (*fp->_close)(fp->_cookie);
146 /* Get a new descriptor to refer to the new file. */
147 f = _open(file, oflags, DEFFILEMODE);
148 if (f < 0 && isopen) {
149 /* If out of fd's close the old one and try again. */
150 if (errno == ENFILE || errno == EMFILE) {
151 (*fp->_close)(fp->_cookie);
153 f = _open(file, oflags, DEFFILEMODE);
160 * Finish closing fp. Even if the open succeeded above, we cannot
161 * keep fp->_base: it may be the wrong size. This loses the effect
162 * of any setbuffer calls, but stdio has always done this before.
165 (*fp->_close)(fp->_cookie);
166 if (fp->pub._flags & __SMBF)
167 free((char *)fp->_bf._base);
171 fp->_bf._base = NULL;
173 fp->pub._lbfsize = 0;
180 memset(WCIO_GET(fp), 0, sizeof(struct wchar_io_data));
182 if (f < 0) { /* did not get it after all */
183 fp->pub._flags = 0; /* set it free */
185 errno = sverrno; /* restore in case _close clobbered */
190 * If reopening something that was open before on a real file, try
191 * to maintain the descriptor. Various C library routines (perror)
192 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
194 if (wantfd >= 0 && f != wantfd) {
195 if (_dup2(f, wantfd) >= 0) {
201 fp->pub._flags = flags;
205 fp->_write = __swrite;
207 fp->_close = __sclose;
209 * When opening in append mode, even though we use O_APPEND,
210 * we need to seek to the end so that ftell() gets the right
211 * answer. If the user then alters the seek pointer, or
212 * the file extends, this will fail, but there is not much
213 * we can do about this. (We could set __SAPP and check in
216 if (oflags & O_APPEND)
217 _sseek(fp, (fpos_t)0, SEEK_END);